Examples of the secondary battery include a nickel-metal hydride battery, a lead-acid battery, and a lithium-ion secondary battery.
Such secondary batteries are used as power sources in portable information terminals typified by mobile phones. In particular, lithium-ion secondary batteries have been actively researched and developed because capacity thereof can be increased and size thereof can be reduced.
Patent Document 1 discloses that a multilayer graphene flake or multilayer graphene flakes are wrapped around positive electrode active material particles or negative electrode active material particles to prevent dispersion of the positive electrode active material particles or the negative electrode active material particles and collapse of a positive electrode active material layer or a negative electrode active material layer. Multilayer graphene can maintain the bond to the positive electrode active material particles or the negative electrode active material particles.